The present invention relates generally to accessing storage media, and more particularly without limitation to systems and methods compensating for head assembly polarity in relation to accessing storage media.
Various storage media are used to store information. In a typical implementation, data is written to and read from a disk using a read/write head assembly that is disposed near the surface of the disk. In an effort to increase the potential information storage density, the geometry of the head assemblies have been substantially reduced and materials used to form the head assemblies have changed. While these advancements have allowed for increased data storage, they have also resulted in various undesirable affects. For example, the polarity of head assemblies is known to invert. When the polarity of a head assembly inverts, the signal read back from the disk is inverted from the expected polarity. This results in an inability to read data from the disk.
Some solutions to this problem include providing a user selectable switch that allows a user to invert the head assembly when the user notices a number of read errors. This may be an effective solution where polarity inversion is very infrequent. However, this solution is not effective where inversion of the head assembly happens more than once or twice in the lifetime of the head assembly. Another solution automatically switches the polarity of the head assembly after a period of failed reads is detected. After the period of failed reads, the polarity of the head assembly is inverted. While this solution is automatic, it can have a devastating impact on the rate at which data from a disk can be read. Further, this impact may be highly unpredictable where the frequency at which the head assembly is changing polarity is variable. Yet another solution replicates a substantial portion of the pattern detection circuit—using an original portion of the pattern detection circuit to operate on non-inverted data and the replicated portion to operate on inverted data. Where the original portion of the circuit identifies the pattern the head is considered to be non-inverted. In contrast, when the replicated portion identifies the pattern, the head is considered to be inverted. While effective, such an approach is expensive both in terms of semiconductor area and power consumption.
Hence, for at least the aforementioned reasons, there exists a need in the art for advanced systems and methods accessing data using a variable polarity head assembly.